Interesting comment from Paco R: Do tune sessions have a 'tradition' at all?

I don't know - but what appears to be coming across from comments to this thread at the moment is that, once you move away from songs to instrumental music, there seems to be a more relaxed approach to the concept of 'tradition'. Interesting. I recall hearing "Yesterday" played as a guitar instrumental at a few folk sessions when it first appeared around 1965. And the other one sometimes played in the clubs was MacCartney's "Blackbird" - mind you, a little riff nicked from a Bach Bourrée can go a long way... 300 years perhaps, and we'll hear them at sessions?